From patchwork Thu Jan 30 21:35:45 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13954998 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8BC0814A099; Thu, 30 Jan 2025 21:36:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738272972; cv=none; b=rbnbRA8MWpuTx7R+niCbVIWVUNil5huk/7coxSmiKTQu7hqJ/D7PQyfBKyhc9dxbucGbZc1i2DH3nKaITZCNYZQ0asxCXfTd/mvTgvzqzDLQ2RhHDUW/okUpP4EMuMuaqv+2CEuMWUxCQ1cO6DwBW18RiPXFL7lhUjJqOhvHryM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738272972; c=relaxed/simple; bh=H5GEx+worDd8tB0hkG/tnGIycbOtMqFJiMcNHVGYbAg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=R5gBdH4kUOUJeRbNje7tMQGDQCPnO5A80rVKT6epmCJ5IEWxjICemz2TEE1nTUoLxp9VI6RXJWE0aRI38gKysSrToDdIaZpuAO5b8JPBA3f7HjaPyzwnSVvn7b4gsLpMJ/4BxygyjJTB9Fngf4GXon/Hy8B6ajEVXuSRd89G0l4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gSq0tlZc; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gSq0tlZc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43C76C4CED2; Thu, 30 Jan 2025 21:36:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738272972; bh=H5GEx+worDd8tB0hkG/tnGIycbOtMqFJiMcNHVGYbAg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gSq0tlZcFjt0M1rEcgtaYubNvkS1fwJbfOyx7yn+uzpX9pkEtRUKeLpPx7WuCu12P h0LflgONVcvUNQ16N24hgPJCX7t7v/sOLBmFen7juLG5SLNrZa6l/bjOnVWgnS6Vq5 MIp1EmCtxw74o7Ch0Ya24YuO6G/JaOgacM/NG/ezbJADWj98lNlK6Ud5dQ0tYrNEg4 8SYke/ZaaD9nxdK+yWGBZ5R0RQOQ5rH067isKl86vrH9uG+RBLvo0zWeDCp4SgY/3e TbGABph9a/v5Isw5Y+vw/4UeBz8LI99GCja4CEbXxIrWPF5oYqbH954oFS/XTQgIAF GwjCPfOvelpEg== From: Song Liu To: bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Cc: kernel-team@meta.com, andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, kpsingh@kernel.org, mattbobrowski@google.com, liamwisehart@meta.com, shankaran@meta.com, Song Liu Subject: [PATCH v12 bpf-next 1/5] fs/xattr: bpf: Introduce security.bpf. xattr name prefix Date: Thu, 30 Jan 2025 13:35:45 -0800 Message-ID: <20250130213549.3353349-2-song@kernel.org> X-Mailer: git-send-email 2.43.5 In-Reply-To: <20250130213549.3353349-1-song@kernel.org> References: <20250130213549.3353349-1-song@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Introduct new xattr name prefix security.bpf., and enable reading these xattrs from bpf kfuncs bpf_get_[file|dentry]_xattr(). As we are on it, correct the comments for return value of bpf_get_[file|dentry]_xattr(), i.e. return length the xattr value on success. Signed-off-by: Song Liu Acked-by: Christian Brauner Reviewed-by: Jan Kara Reviewed-by: Matt Bobrowski --- fs/bpf_fs_kfuncs.c | 36 +++++++++++++++++++++++++----------- include/uapi/linux/xattr.h | 4 ++++ 2 files changed, 29 insertions(+), 11 deletions(-) diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c index 3fe9f59ef867..db5c8e855517 100644 --- a/fs/bpf_fs_kfuncs.c +++ b/fs/bpf_fs_kfuncs.c @@ -93,6 +93,24 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz) return len; } +static bool match_security_bpf_prefix(const char *name__str) +{ + return !strncmp(name__str, XATTR_NAME_BPF_LSM, XATTR_NAME_BPF_LSM_LEN); +} + +static int bpf_xattr_read_permission(const char *name, struct inode *inode) +{ + if (WARN_ON(!inode)) + return -EINVAL; + + /* Allow reading xattr with user. and security.bpf. prefix */ + if (strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) && + !match_security_bpf_prefix(name)) + return -EPERM; + + return inode_permission(&nop_mnt_idmap, inode, MAY_READ); +} + /** * bpf_get_dentry_xattr - get xattr of a dentry * @dentry: dentry to get xattr from @@ -101,9 +119,10 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz) * * Get xattr *name__str* of *dentry* and store the output in *value_ptr*. * - * For security reasons, only *name__str* with prefix "user." is allowed. + * For security reasons, only *name__str* with prefixes "user." or + * "security.bpf." are allowed. * - * Return: 0 on success, a negative value on error. + * Return: length of the xattr value on success, a negative value on error. */ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__str, struct bpf_dynptr *value_p) @@ -114,18 +133,12 @@ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__st void *value; int ret; - if (WARN_ON(!inode)) - return -EINVAL; - - if (strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) - return -EPERM; - value_len = __bpf_dynptr_size(value_ptr); value = __bpf_dynptr_data_rw(value_ptr, value_len); if (!value) return -EINVAL; - ret = inode_permission(&nop_mnt_idmap, inode, MAY_READ); + ret = bpf_xattr_read_permission(name__str, inode); if (ret) return ret; return __vfs_getxattr(dentry, inode, name__str, value, value_len); @@ -139,9 +152,10 @@ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__st * * Get xattr *name__str* of *file* and store the output in *value_ptr*. * - * For security reasons, only *name__str* with prefix "user." is allowed. + * For security reasons, only *name__str* with prefixes "user." or + * "security.bpf." are allowed. * - * Return: 0 on success, a negative value on error. + * Return: length of the xattr value on success, a negative value on error. */ __bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__str, struct bpf_dynptr *value_p) diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h index 9854f9cff3c6..c7c85bb504ba 100644 --- a/include/uapi/linux/xattr.h +++ b/include/uapi/linux/xattr.h @@ -83,6 +83,10 @@ struct xattr_args { #define XATTR_CAPS_SUFFIX "capability" #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX +#define XATTR_BPF_LSM_SUFFIX "bpf." +#define XATTR_NAME_BPF_LSM (XATTR_SECURITY_PREFIX XATTR_BPF_LSM_SUFFIX) +#define XATTR_NAME_BPF_LSM_LEN (sizeof(XATTR_NAME_BPF_LSM) - 1) + #define XATTR_POSIX_ACL_ACCESS "posix_acl_access" #define XATTR_NAME_POSIX_ACL_ACCESS XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_ACCESS #define XATTR_POSIX_ACL_DEFAULT "posix_acl_default"